Again, you need to ask your school. If they can’t help you then next you can contact College Board about taking it elsewhere. There’s no reason why you shouldn’t be able to sign up for an AP test at your school even if not enrolled for the course, students do it all the time. The late fee is the issue. Many schools however, due to covid are definitely being more flexible since they don’t know if tests are going to be administered in person or not, even though College Board is planning in person. We haven’t even paid for our school yet and normally the fees were due months ago. They’re also letting us cancel right up to the day of the test this year, once we do pay, which normally there is a penalty to do so. Every school will handle it different though and since we don’t work at your school, we can’t really answer. They need to have proctors to monitor you if in person if no one else is taking that Exam, as well as order it, so I would email the AP administrator at your school as soon as vacation end.
If school can’t order it, another option is to see if the college you’re planning to attend has placement tests you can take, or if they accept CLEP exams.